When we choose the processing technology of our products, we often consider the question “Which is better, thermoforming or injection molding?” However, there is no one-size-fits-all answer, as the choice of process often depends on the design and functional requirements of the product. Thermoforming and injection molding are two common plastic molding processes that use different methods when making plastic parts and products. Thermoforming is suitable for products that require special appearance, transparency, and complex shapes, while injection molding is suitable for projects that require high precision and large-scale production. How to choose a suitable processing technology, you can make a decision through the following analysis.

What Is Thermoforming?

Thermoforming is a versatile plastic manufacturing process that involves heating a thermoplastic sheet until it becomes flexible and pliable, and then shaping it around a custom-designed tool. This tool, typically made from cost-effective aluminum, allows for the creation of various plastic parts and products with reduced initial costs.

At Sungplastic, we offer three different types of thermoforming: vacuum forming, pressure forming, and twin sheet forming. Understanding these thermoforming methods allows us to select the most appropriate process for your specific needs, balancing design complexity, cost-effectiveness and production efficiency.

Vacuum Forming

Vacuum forming entails pressing the heated plastic sheet against a mold while vacuuming out the air to achieve a snug fit against the mold surface. It is the fastest and most cost-effective method for forming plastics. Vacuum forming is best suited for creating large parts that do not require intricate detailing, sharp corners, or precise angles.

Pressure Forming

In contrast to vacuum forming, pressure forming involves heating the plastic and wrapping it around the tool, followed by a blast of highly pressurized air to force the plastic against the tool. This process is ideal for achieving sharp corners and intricate details that vacuum forming may not provide.

Twin-Sheet Forming

Twin-sheet forming employs two sheets of heated plastic pressed against a single mold from opposite sides, fusing where both sheets meet. This technique is often used to produce air ducts, vending machines, bed liners, and hollow or double-walled industrial products. Twin sheet forming requires meticulous precision to ensure the pieces are properly aligned and fused with utmost accuracy.

What Is Injection Molding?

Injection molding is a highly versatile and widely used manufacturing process in which thermoplastic or thermosetting plastic materials are melted and then injected into a custom-designed mold, often under high pressure. Once inside the mold, the molten plastic material takes on the shape of the mold cavity as it cools and solidifies. This process allows for the mass production of plastic parts and products with high precision and consistency.

Key Features of Injection Molding:

    • High Precision:
      Injection molding offers unparalleled precision, ensuring that even the most complex and detailed parts are replicated with remarkable accuracy.
    • Variable Thickness:
      This method allows for the creation of components with varying wall thicknesses, a feature crucial for many applications.
    • Intricate Details:
      Injection molding can reproduce intricate features, textures, and designs on the surface of the molded parts, making it ideal for products requiring fine detailing.
    • Sharp Corners and Angles:
      The process excels at producing parts with sharp corners and precise angles, delivering consistent results.
    • Small Plastic Parts:
      Injection molding is highly efficient for producing small to medium-sized plastic components, where tight tolerances and consistent quality are essential.

Thermoforming VS. Injection Molding: Cost and Lead Time

Next, we analyze the differences between thermoforming and injection molding in terms of cost and lead time.

Cost of Thermoforming VS. Injection Molding

    • Thermoforming typically incurs significantly lower upfront costs compared to injection molding. This cost difference can be attributed largely to the tooling requirements of each process. Thermoforming benefits from using aluminum for tooling, a cost-effective material, because the pressure involved is much less than that of injection molding. Moreover, crafting a single-sided tool for thermoforming is simpler and more economical when compared to the creation of molds necessary for injection molding.
    • On the other hand, injection molding necessitates robust dual-sided molds capable of withstanding pressures of up to 530 tons. These molds are crafted from pricier materials such as steel, heavier aluminum, or beryllium-copper alloy. However, it’s important to note that once the tooling for injection molding is produced, it can be reused, making this method more cost-effective for large production runs or recurring orders.

Lead Times with Thermoforming VS. Injection Molding:

    • Thermoforming typically boasts shorter lead times in comparison to injection molding, largely due to differences in tooling design and fabrication. The process of designing and prototyping a single-sided aluminum tool is significantly faster than creating a complex, dual-sided 3D mold employed in injection molding. At API, lead times for thermoforming, spanning from design and development to delivery, typically average around 14 weeks. In contrast, injection molding may take up to 20 weeks, primarily due to the time-consuming tooling design and production phase.
    • It’s worth noting that the tooling investment in injection molding is a one-time occurrence; subsequent runs benefit from reduced lead times and per-unit costs, making it a more cost-effective choice for ongoing or large-scale production.

Selecting Thermoforming VS. Injection Molding

As previously mentioned, neither method holds a superiority over the other; the choice between thermoforming and injection molding ultimately depends on achieving the most precise plastic product at the lowest cost within the shortest timeframe.

Selecting Thermoforming

Thermoforming is typically the preferred choice when:

    • Larger Plastic Parts: You require larger plastic components or need to consolidate multiple elements into a single part.
    • Smaller Orders: Your order size falls below 3,000 pieces, or it’s a one-time production run.
    • Simplified Design: The final product doesn’t demand intricate design, variable thickness, sharp angles, or corners.

Selecting Injection Molding

Injection molding is generally the more suitable option when:

    • Smaller Plastic Parts: You need smaller plastic parts for your project.
    • Large Orders: You anticipate large orders or frequent production runs.
    • Complex Components: The component requires high levels of detail, variable thickness, and precise, sharp corners and angles.

Sungplastic Helps You Choose the Right Processing Technology

After the previous analysis, you should have a preliminary understanding of the difference between thermoforming and injection molding. Both machining processes have their own advantages, and the final choice depends on the specific needs of your project, including size, design requirements, and delivery time. Our goal is to help you get high-quality plastic parts and products in the shortest time at the lowest cost.

Sungplastic is an experienced plastic product manufacturer, we provide professional thermoforming and injection molding services. At Sungplastic, our team of engineers will assist you every step of the way, from mold design and material selection to assembly and packaging of finished products to ensure you are provided with the perfect solution. Contact us today to get an instant quote and let’s get started on your project together.

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